Operative retreating around soldiers in battle (5)
I believe the answer is:
ypres
'battle' is the definition.
(Ypres is an example)
'operative retreating around soldiers' is the wordplay.
'operative' becomes 'spy' (I've seen this in another clue).
'retreating' is a reversal indicator.
'around' means one lot of letters goes inside another.
'soldiers' becomes 're' (Royal Engineers).
'spy' backwards is 'yps'.
'yps' placed around 're' is 'YPRES'.
'in' is the link.
(Other definitions for ypres that I've seen before include "WWI battlefield" , "WW1 battle town" , "WW1 battle site" , "Scene of action" , "Belgian town" .)